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Imperial bolt question...

Featured Replies

34 minutes ago, b40rt said:

Minor hijack, any one found a source for Allan button top bolts ?

They're very common in the US, often called "button-head cap screw" or "socket button head".

‘Like a bolt out of the blue’ The Shank of a bolt was supposed to take the shear load i.e. a swinging shackle bolt for leaf suspension. Most bike engine bolts use the shank to carry the load of the engine, the threaded portion maintains a clamping force to prevent movement in the mountings. Simples innit?‍?

3 hours ago, konrad said:

They're very common in the US, often called "button-head cap screw" or "socket button head".

Thanks konrad, common here to if you want set screws, but not as bolts. 

28 minutes ago, b40rt said:

Thanks konrad, common here to if you want set screws, but not as bolts. 

My mistake, I'll blame my poor English skills.

In the US, McMaster-Carr  https://www.mcmaster.com/standard-rounded-head-screws has been a great reference source for as long as I can remember.

They say "fully threaded" or "partially threaded" (which is far less common).

3 hours ago, konrad said:

My mistake, I'll blame my poor English skills.

In the US, McMaster-Carr  https://www.mcmaster.com/standard-rounded-head-screws has been a great reference source for as long as I can remember.

They say "fully threaded" or "partially threaded" (which is far less common).

Appreciate your input, I've yet to find any "partial threaded" I'm assuming its because the relatively small allen key size isn't sufficient for proportionate torque ?

1 hour ago, b40rt said:

Appreciate your input, I've yet to find any "partial threaded" I'm assuming its because the relatively small allen key size isn't sufficient for proportionate torque ?

Not sure I understand your question.  The key size is based on the diameter. The tightening torque is a function of several parameters (e.g., grade, diameter, pitch) but length really does not enter into it.  Are you looking for a specific bolt?

 

44 minutes ago, konrad said:

Not sure I understand your question.  The key size is based on the diameter. The tightening torque is a function of several parameters (e.g., grade, diameter, pitch) but length really does not enter into it.  Are you looking for a specific bolt?

 

Yes, m8 for bottom shock mounts on twin shocks. No real stress on these, button tops don't tend to get snagged on passing scenery ?

2 hours ago, b40rt said:

Yes, m8 for bottom shock mounts on twin shocks. No real stress on these, button tops don't tend to get snagged on passing scenery ?

Everything I saw has a minimum threaded length of 28mm.  So if you needed, say, 25mm unthreaded, you would buy a 55mm fastener and cut off most of the threads.

This example is stainless, with a 70 ksi tensile strength: https://www.mcmaster.com/92095a299

That's soft enough that, I think, you could cut more threads with a die.  But that's generally frowned upon.  And using a spacer under the head would would circumvent what you are trying to achieve with the button head.

How about some sort of slippery plastic covering over the original bolt head?

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